Multimeter range overflow far below adjusted limit

[tklosa]

I try to measure small voltages and have here a case where I get an unexpected range overflow using the virtualbench PC Application.

10V Range: Value is 0,0032V

1V Range: Value is 003,24mV

100mV Range: The german version displays >Bereich, what is a range overflow.

The voltage source is an instrumentation amplifier. The meter input impedance should not change my voltage. I'm sure it's still 3,2mV

[tklosa]

An OpAmp stage in front of the instrumentation amp was oscillating. As a result of that the output signal must have had a considerable AC on top of the DC.

For pure DC it is working. However, it is somehow strange that my other meters did display the DC average for this signal.